I am looking to start a discussion on possible causes for a comp failure.
This job is a nightmare. I will be going there Monday to resolve issue and I am just looking to spitball some ideas. Unfortunately for me I have limited involvment on this job and much of the info I have is hear-say from other mechanics.
3 comp rack system, R22 system, ICP style CPC controller that is only being used to monitor and cycle compressors and unloders. 3 ckt's being temp controlled with LL solenoid valves. High temp system 68 degree set point. Defrost is probably electric but have not had enough time on equipment to say for sure, defrost settings are also unknown at this point. Acct is a tomatoe packing plant and refrigeration ckts are not in constant use. Often 1 or more boxes are empty and those sys's are left in a pumped down state. Oil system is using temprite, check valve (differental needs to be checked), oil resivior level unknown, comp's are hooked up with oil equalizing line.
The original call was for 2 compressors offline. 1st comp held off at oil safety (Penn Mechanical). Cleaned P/U tube and started up fine 20 psig differental. 1/2 glass of oil at pot. Oil lil foamy might have liquid refrigerant laying in oil?
2nd comp had thrown rod. This compressor was replaced but contactors were not. Contactors are pitted but are worn. Obviously they should of been replaced (6 wire 2 contactor wiring configuration) Amp draw was aprox 35 amps on each leg at start up under full load, RLA is 60 amps.
New comp ran 1 week and then shorted to ground. 1st compressor off on tripped oil safety. Oil dark but not gritty in rack. Pulled P/U tube and inspected (clean) also keeping 20psig crankcase differental. Oil safety bad and will replace on Monday. Also found and replaced failed phase monitor.
Tech dispatched to site next morning observed heavy sweatback on 3rd comp (possibly flooding back?). New comp sat overnight calling but held out by open in control circuit. Determined to be held off at control module in peckerhead. Line voltage feeding comp was removed, control mod jumped, contactor pulled in. Shut down circuit, put line voltage back, restarted, never observed comp run, Comp had 2 legs shorted to ground, did not check windings prior to starting, possible it was shorted out of the box???
Also CPC board had intermittent supply power problem. Loose wires seemed to be culprit and has been resolved.
So thats what I am up against
Heres my Monday morning game plan:
1. change out comp again
2. check SH @ txv's and @ comp's
3. check LL soleinoid valves for bleed-by
4. acid test
5. considering oil viscosity test
6. if acid change out cores on LL and also put in suctionm cores for clean up.
My thought is that because this rack keeps such a high temp setpoint that the sweating my be indicating a fllodback issue. Foam in oil may indicate liquid in oil. Flooded start conditions may be cause of problem along with bearings being washed out.
I got myself a full plate on Monday and any thoughts or ideas anyone has would be welcomed. Sorry for the lack of specifics on equipment data I will have that stuff once I get onsite.